Structural and bonding aspects of copper coordination in doped amino acid single crystal systems were obtained by a series of collective relationships between parameters measured by EPR, ENDOR and ESEEM, and copper-site geometries inferred from previous diffraction studies of these systems. An analysis was undertaken of EPR and ENDOR (or ESEEM) results from previous and current studies of six Cu(II)-doped amino acid single crystal systems. Correlations are found between various geometric features derived from crystallographic results of these host systems and magnetic coupling interactions of amino group or imidazole 14N and 1H (or 2D) attached to the amino group and C, with the unpaired electron spin.